Electric Double Layer Capacitor - is a next-generation energy storage device that will be used as an auxiliary power supply and the combined use with photovoltaics equipment and hybrid electric cars, also known as supercapacitors or ultracapacitors, have very high capacitance values but low voltage ratings. They use a molecule-thin layer of electrolyte, rather than a manufactured sheet of material, as the dielectric. As the energy stored is inversely proportional to the thickness of the dielectric, these capacitors have an extremely high energy density. The electrodes are made of activated carbon, which has a high surface area per unit volume, further increasing the capacitor's energy density.